1. Field of the Invention
The present invention relates to a semiconductor memory device, for example, one in which a dynamic memory is used for the main memory thereof.
2. Description of the Prior Art
The DRAM (Dynamic Random Access Memory) of prior art that makes use of a dynamic memory has always been designed as a device that requires repeated refreshing to keep data stored for the necessary duration of time.
However, such refresh control has been a task the user is responsible for, so the user must design a proper refresh control circuit at the stage of system design. This is a burden on the user. Such control circuit operates solely under control of a signal given from exterior. Further, the refresh mode in which data can neither be read nor rewritten lowers the efficiency of DRAM utilization.